Niemitz (1984) synonymized three of Hill’s (1955) Tarsius spectrum subspecies (the forms sangirensis, dentatus, and pelengensis) with T. s. spectrum. Feiler (1990) argued for the resurrection of T. sangirensis as a distinct species, an opinion that was independently supported by Shekelle et al. (1997) and Groves (1998). See Groves (2003).

Shekelle and Salim (2009) used remote sensing to estimate the population size to be between 1,505 and 52,734 individuals, the very wide range being a result of uncertainty in the suitability of "brush" habitat for sustainable tarsier populations. Without including "brush", the population size estimate is only 1,505–2,795 individuals. Riley (2002) estimated population size as 9,000–15,600, but those numbers drop to 300-500 if secondary habitat is excluded. Riley did not address the issue that, while tarsiers are recorded in secondary habitats, these might not support sustainable populations. Thus, the conclusions of both studies are similar; viable population size might be very small indeed, unless populations in suboptimal habitats are "sources" and not "sinks".

This population has not been studied systematically in the wild, but was surveyed by Shekelle and associates (Shekelle et al. 1997, Shekelle 2003) and Riley (2002). Riley remarked that T. sangirensis has a preference for primary forest, but may occur in secondary habitats including sago swamps, scrub, nutmeg plantations, coconut plantations, and secondary forest growth. These results are similar to those of Shekelle and associates, except that Shekelle did not encounter any in primary forest, and Shekelle and Salim (2009) indicate that it is very unlikely that any primary forest now remains on the island. A study of Tarsius dentatus on Sulawesi by Merker et al. (2005, also Merker and Yustian 2008) showed that they were able to occupy agricultural land as long there were remnant patches of forest or dense shrubbery, although group sizes were smaller and population densities were considerably lower (less than half) than was found for virtually undisturbed old-growth forest (estimated densities 268 individuals/km² vs. 45 individuals/km²).

Like other Eastern Tarsier species from the Sulawesi biogeographic region, this species lives in small, monogamous or polygamous groupings of 2–6. It might sleep in dispersed social groups, particularly in disturbed habitat, and that this might be a response to predation, particularly by humans and human commensals, such as feral cats and dogs. Merker (2006) studied home range size in T. dentatus and found it to vary, depending on the degree of human disturbance, with home range size increasing with the degree of disturbance. Its diet is mostly large arthropods and some small vertebrates.

Shekelle and Salim (2009) argue that the chief threat to tarsiers on Sangihe Island is habitat loss. One major driver of habitat loss is the clearing of forests and forest gardens for more intensive agriculture where underbrush is cleared, such as coconut monocrop, coconut/chocolate, nutmeg, and others (M. Shekelle pers. comm. 2010). Riley (2002), however, did not think that habitat loss was a major threat, given their presence in a variety of secondary habitats. This discrepancy emphasizes the need to determine the suitability of secondary habitats for sustainable tarsier populations. The volcano on Sangihe Island, Mt Awu, is active and one of the deadliest in Indonesia, and the human population density on the island is very high (260 people km-²) (Shekelle and Salim 2009). There is practically no primary forest left and there are no protected areas in its range (Shekelle and Salim 2009).

The taxon has been protected by national law since 1931, and is listed in CITES Appendix II. Two conservation initiatives begun in 2002 are serving to establish management systems on this archipelago and to educate its people on the environmental and conservation problems that the islands face, including those resulting from forest management and hunting (Riley 2002) (see Whitten 2006).

In-Place Research, Monitoring and PlanningIn-Place Land/Water Protection and ManagementIn-Place Species ManagementIn-Place Education Subject to recent education and awareness programmes:Yes Included in international legislation:Yes Subject to any international management/trade controls:Yes